Do .blend files store information on which version of Blender they were created in?
Open the .blend file in any text editor, the first few characters will be something like this (followed by a lot of unreadable binary data which you can ignore):

BLENDER-v267

That's the version number right there, this file would have been saved with Blender 2.67.

If it's not there, that probably means you are looking at a compressed .blend file. In that case you can rename the file to have the extension .blend.gz and decompress it. Note that resaving from Blender doesn't work because the version number would change.